Exemplary embodiments of the invention relate to a divided toothed wheel having two toothed wheel halves braced against each other, wherein the first toothed wheel half comprises a hollow cylindrical collar, to which the second toothed wheel half is attached by a fastening element.
In the case of shafts driven via a toothed wheel drive, e.g. camshafts or compensating shafts, which in operation rotate at half or double the engine speed, it is known to use a divided toothed wheel having toothed wheel halves braced against each other as the drive element instead of simple one-piece toothed wheels. The play-free bracing of the toothed wheels avoids undesired noise propagation, which could occur, as experience has shown, when using one-piece toothed wheels because some play exists.
EP 0 205 156 B1 discloses a divided toothed wheel which consists of a first toothed wheel part and a second toothed wheel part, wherein the toothed wheel parts are braced against each other via an omega-shaped spring. The first toothed wheel part comprises a hollow cylindrical spigot-shaped collar with which it can be pushed onto a shaft and which surrounds the shaft in the mounted condition. The second toothed wheel part is pushed onto the outer periphery of the collar during mounting. The collar comprises a groove on its outer periphery, into which a snap ring is inserted, with which the second toothed wheel part is attached to the collar in an axially positive locking manner. The second toothed wheel part is supported, with its side surface facing away from the first toothed wheel part, against the snap ring.
In the figures of EP 0 205 156 B1 the snap ring is not shown. The attachment of the second toothed wheel half to the collar is merely described in the descriptive part and not shown in the drawing.
If the snap ring is removed from the groove, the second toothed wheel part can be pulled off the collar. The two toothed wheel parts are thus not connected to each other in a non-releasable manner, but rather the second toothed wheel half is merely held on the collar by a releasable positive locking connection.
A disadvantage with this known connection between the two toothed wheel halves is also that, as seen in the axial direction of the shaft, a large construction space is required because, as seen in the axial direction, the collar of the first toothed wheel half must protrude clearly beyond the side surface of the second toothed wheel half, which faces away from the first toothed wheel half, so that the groove can be produced in the collar and at the same time sufficient “substance” is also still provided at the free end of the collar in order for the collar to have the necessary strength. However, in particular in the case of camshafts or compensating shafts in internal combustion engines, the designers frequently allow only a very small construction space.
In view of the known toothed wheel discussed above, exemplary embodiments of the present invention provide a divided toothed wheel with two toothed wheel halves braced against each other, in which, as seen in the axial direction, only a minimum amount of construction space is taken up and the two toothed wheel halves are non-releasably connected to each other.
Exemplary embodiments of the present invention also provide a simple process for assembling a divided toothed wheel with two toothed wheel halves which are braced against each other, wherein, as seen in the axial direction, the two toothed wheel halves can be non-releasably connected to each other in the most space-saving manner possible.
The divided toothed wheel in accordance with the invention has two toothed wheel halves which are braced against each other, wherein the first toothed wheel half has a hollow cylindrical collar with a groove, on which collar the second toothed wheel half is attached in an axially positive locking manner by a fastening element inserted into the groove. In accordance with the invention the second toothed wheel half has a radially extending recess, and the fastening element is formed as an elastically deformable spring ring which is disposed in a receiving space defined by the groove and the recess, and connects the two toothed wheel halves to each other in a non-releasable manner. Therefore, in accordance with the invention, the two toothed wheel halves that are to be connected to each other have mutually corresponding recesses to receive the spring ring and, when the toothed wheel halves are in the assembled condition, the spring ring connects the toothed wheel halves in a positive locking and non-releasable manner. The connection is non-releasable because the second toothed wheel half cannot be pulled off the collar without destroying the spring ring and/or the second toothed wheel half.
According to an embodiment of the invention, the recess in the second toothed wheel half is formed as a relief groove that is open towards a side surface of the second toothed wheel half. This relief groove can easily be turned in the second toothed wheel half as a cut turning. When the toothed wheel halves are in the assembled condition, the recess in the second toothed wheel half overlaps with the groove disposed in the collar of the first toothed wheel half. In this way the groove in the collar and the recess in the second toothed wheel half form a receiving space open to the surroundings, in which receiving space the spring ring is disposed.
The spring ring does not protrude—or only minimally protrudes—in the axial direction beyond the side surface of the second toothed wheel half, which faces away from the first toothed wheel half. Therefore, in comparison to the connection—known from the prior art discussed above—with the snap ring disposed axially outside the second toothed wheel half, the joint region, i.e., the region in which the positive locking connection between the two toothed wheel halves is produced, is shifted into a region that is located below the second toothed wheel half. The collar of the first toothed wheel half therefore possibly has to protrude beyond the second toothed wheel half in the axial direction only to a minimum extent in order to ensure the required strength for the collar. The construction space required in the axial direction is thus minimized.
According to another embodiment of the invention the space receiving the spring ring is not open to the surroundings but is formed as a closed receiving space which is formed by the grooves overlapping each other in the assembled condition, which grooves are disposed on the one hand in the collar of the first toothed wheel half and on the other hand in the second toothed wheel half. In order to achieve this, the recess in the second toothed wheel half is formed as a groove disposed between the two side surfaces of the second toothed wheel half. When the divided toothed wheel is in the assembled condition the spring ring producing the positive locking connection cannot be seen from the outside. It is totally covered by the second toothed wheel half and does not protrude beyond its side surface facing away from the first toothed wheel half. In this embodiment of the invention the spring ring is no longer accessible from the outside once assembly is complete. The second toothed wheel half cannot then be pulled off without the spring ring and/or the second toothed wheel half and/or the collar being destroyed. The construction space required in the axial direction is accordingly minimized to a considerable degree in this embodiment.
In both embodiments of the invention the spring ring can be formed in a cost-effective manner as a simple wire flexing part.
The process in accordance with the invention for assembling a divided toothed wheel with two toothed wheel halves braced against each other starts with a first toothed wheel half which has a hollow cylindrical collar with a groove. A second toothed wheel half is pushed onto the collar, wherein the second toothed wheel half is attached in an axially positive locking manner to the collar by a fastening element that is inserted into the groove. In accordance with the invention, in the second toothed wheel half a radially extending recess is provided which at least partially overlaps with the groove when the toothed wheel is in the assembled condition, and before the second toothed wheel half is pushed onto the collar an elastically deformable spring ring is inserted into the groove, which spring ring is elastically deformed by the second toothed wheel part during this pushing movement in such a way that the second toothed wheel half can be pushed onto the collar until it reaches the joint position, wherein, upon the joint position being reached, the spring ring springs back into the recess thus forming the axially positive locking connection.
With the process in accordance with the invention a non-releasable connection between the two toothed wheel halves can easily be produced and only minimum construction space is required in the axial direction. The assembled two-part toothed wheels can therefore be produced and have a clearly smaller axial extension than the known toothed wheels discussed above. In particular, when used in internal combustion engines, e.g. on camshafts or compensating shafts, construction space can be saved in this manner or available construction space can be optimally exploited.